Equilibrium Dialysis

Equilibrium dialysis is a specific
application of dialysis that is
important for the study of the
binding of small molecules and
ions by proteins. It is one of several
methods available for this
purpose, and its attractive feature
continues to be its physical
simplicity. Another attractive feature
of equilibrium dialysis is the
ability to perform interaction
studies without the use of fluorescent
or radiolabeled tags.

Generally, the objective of an equilibrium dialysis experiment is to
measure the amount of a ligand bound to a macromolecule. This is
typically done through an indirect process because in any mixture of
the ligand and macromolecule, it is difficult to distinguish between
the bound and free ligand. If, however, the free ligand can be
dialyzed through a membrane, until its concentration across the
membrane is at equilibrium, the free ligand concentration can be
measured easily. Data obtained under different experimental
conditions then provides information on various binding parameters
of the compounds such as the binding constants and the number of
binding sites or binding capacity.